This invention relates generally to gas turbine engines and more particularly to apparatus for venting gear boxes in gas turbine engines.
A gas turbine engine usually includes one or more mechanically-driven accessories, such as fuel or oil pumps, generators or alternators, control units, and the like. Such accessories are mounted to an accessory gearbox (“AGB”) which extracts torque from the engine, and drives each accessory at the required rotational speed, using an internal gear train.
Pressurized oil flow is delivered to the AGB for lubrication and cooling. The spent oil from the AGB drains back to a supply and scavenging system of the engine. In a typical configuration, one or more engine sumps are vented through a rotating air-oil separator located on the alternator drive shaft in the AGB. The separated air-oil mixture exits the hollow shaft and enters the vent line which extends from the aft end of the alternator cover.
In prior art engines, the vent line extends in a downhill direction. In such engines, the control of the air-oil mixture relative to potential flooding of internal components is not as critical, because any oil that leaks past internal seals or condenses out of the vent air between the drive shaft and the vent will flow through the downhill vent tube located toward the bottom of the alternator housing, intrinsically limiting the potential amount of oil that might flood the alternator or other AGB components. However, some engine configurations have a vent which must exit the alternator in an uphill direction, which can put the alternator at risk of flooding with oil.
Accordingly, there remains a need for an alternator vent which is not sensitive to the direction of vent air flow.